You should learn both foots because later you'll learn tricks that requiers to have balance on each foots. :)
yes, but keep in mind that one of your feet/legs will always be stronger than the other one, so if you wanna try a new trick and it's hard, you might want to rely on your stronger foot/leg, at least at the beginning.
As riding with both feet is just riding, learning to balance on one foot can help with learning to cross step and do the tricks that come out of that.
You are right.
Короче, просто стой, реально